1. Field of the Invention
This invention pertains to the general field of security ventilating systems for doors and windows in buildings. In particular, it provides a new and improved security screen for use in sliding doors, either as a permanent installation or as a temporary insert for natural ventilation.
2. Description of the Prior Art
People have been using screens in windows and doors for a long time in order to allow natural ventilation from outdoors while keeping insects and other animals outside. During the last few decades, because of an increasing concern with crime and personal safety, these screens have also often served the purpose of keeping intruders from entering the premises. Many different models of ventilation screens have been developed, ranging from the familiar sliding screen-door to the permanent burglar-proof wrought iron bars often found adorning the outside of many residential windows. Similarly, ventilation screens have been built into other functional apparatus, such as pet portals, for use on regular windows and doors, and the same screen concepts have been utilized for applications in other fields, such as in automobile windows.
For example, in U.S. Pat. No. 1,619,501 (1927), Evans discloses an early screen for automobile windows. It is designed to permit ventilation inside the vehicle while avoiding the draft associated with having the windows open during motion. This device is not particularly pertinent to the present invention, but it illustrates a way of affixing a screen structure to a framed opening.
U.S. Pat. No. 3,464,158 to Greene (1969) describes a pet portal for sliding doors that has functional features similar to the invention described herein. The pet portal is built into a vertical panel to be mounted on the tracks of the frame of the sliding door. The panel thus becomes an extension of the frame and reduces the useful travel of the door by a distance equal to its width. Latches on both sides of the panel make it possible to attach it to the jamb of the door frame as well as to the door itself. Thus, the panel can be treated as a permanent extension of the door frame or, if desired, it can be made to slide with the door.
U.S. Pat. No. 3,654,733 to Blackwell (1972) shows a similar pet-door panel for a sliding door frame. The panel insert is essentially the same as the one described above, but it differs in the design of the pet portal. With reference to the insert itself, the same functional features described in Greene are present here.
In U.S. Pat. No. 3,811,224 (1974), Garrison illustrates yet another pet-portal panel design for use as an insert in the frame of a conventional sliding door. This invention is distinguishable on the basis of its specific construction and the configuration of the pet door.
U.S. Pat. No. 4,226,049 to Maust (1980) discloses a security ventilation system that consists of a grille insert for sliding doors, but it is not suitable for use on the tracks of a standard door frame. It requires the permanent mounting of a support structure on the frame and on the sliding door to receive the grille upon use. It also requires the insertion of several screws into the existing door assembly and the drilling of locking stud holes into the frame.
Finally, U.S. Pat. Nos. 4,653,562 to Moss et al. (1987) and 4,913,212 to Clavier (1990) describe two other kinds of automotive safety window screens.
The main problem with existing screens for sliding doors is that they can be easily removed by a potential intruder by lifting them out of the door tracks, thus representing a security hazard for a user. In fact, the level of security required for the psychological comfort of most people is attained only by the installation of permanent bars or of semi-permanent structures, such as the screen shown by Maust. Therefore, there still exists a need for a new and improved, self-contained, security screen that can be quickly inserted into the opening of a conventional sliding door and securely fastened to prevent its unauthorized removal. This invention is directed to the achievement of these goals.